The present invention relates to a method for stabilising a motor vehicle which is decelerated into a rest position and is provided with a service brake and a parking brake which can be actuated independently of the driver, and to a corresponding motor vehicle brake system.
It is already known to provide motor vehicle brake systems with a service brake and a parking brake which can be actuated independently of the driver. For example, EP 0 825 081 B1, and corresponding U.S. Pat. No. 6,019,436 A1, both of which are incorporated by reference herein, describes a brake system of this kind in which the service brake is actuated hydraulically and the parking brake is actuated electromechanically. This means that in a service brake mode, for example when the vehicle is decelerated when travelling, the individual wheels of the vehicle are decelerated by braking devices which are associated with these wheels and can be hydraulically actuated. If, however, the vehicle is parked, i.e. changed over from the service brake mode to a parking brake mode, the parking brake is activated electromechanically, in particular via a self-locking mechanism, and maintained in this parking brake mode until the parking brake mode is actively released. EP 0 825 081 B1 proposes, in the case of a brake system of this kind, that the transition from the service brake mode to the parking brake mode not take place until the braking force which is applied by the parking brake has reached the braking force which is applied by the service brake. It is to be noted in this respect that, where conventional brake systems of this kind are concerned, the parking brake only brakes the rear vehicle wheels, the front vehicle wheels being released unbraked, whereas the service brake acts on all vehicle wheels, that is also on the front wheels. This results in the possibility of complications when there is a transition from the service brake mode to the parking brake mode, in particular when, for example, the roadway surface does not offer sufficient grip in the region of the rear wheels or when, on account of considerable loading or a large trailer load attached to the vehicle, it is impossible to apply sufficiently high braking forces solely through the rear axle in order to hold the vehicle in situ. These problems in the transition from service brake mode to parking brake mode may result in the vehicle sliding or rolling away unnoticed.